For conventional laminates for printed circuit, brominated flame retardants, especially tetrabromobisphenol-A epoxy resin, are usually used to achieve flame retardance. Such brominated epoxy resin has better flame retardancy, but will produce hydrogen bromide during combustion. In addition, carcinogens, such as dioxin, dibenzofuran and the like, have been detected in the combustion products of waste electrical and electronic equipment containing halogens, such as bromide, fluorine and the like. Thus the application of brominated epoxy resin has been limited. Two Environmental Directives, Waste Electrical and Electronic Equipment Directive and The Restriction of the use of certain Hazardous substances in Electrical and Electronic Equipment, were formally implemented on Jul. 1, 2006. The development of halogen-free flame-retardant copper clad laminates became the hot spot in the industry, and the cooper clad laminate manufacturers have launched their own halogen-free flame-retardant copper clad laminates in succession.
With the high speed and multifunctional development of information processing of consumer electronic product, the application frequencies are continuously increased. Besides increasing environmental requirements, there are increasingly requirements on low dielectric constant and dielectric dissipation value. Thus it becomes the hot pursuit to decrease Dk/Df in the substrate industry. For conventional FR-4 materials, dicyandiamide is mostly used as the curing agent. Such curing agent has three-level reactive amine, and has better process operability. However, the cured products have a lower thermal decomposition temperature due to its weaker C—N bond which is easy to split under high temperature, so that they cannot meet the requirements on thermal resistance for lead-free processes. In this context, it began to use phenolic resin as the epoxy curing agent in the industry with the large scale implementation of lead-free process in 2006. Phenolic resin has the benzene ring structure of high density, so that the epoxy-cured system has excellent thermal resistance. However, the dielectric properties of the cured products have the tendency of being deteriorated.